The role of cryptobenthic reef fishes in coral reef trophodynamics

Abstract

An examination of the trophic status of a cryptobenthic reef fish community from the central Great Barrier Reef was carried out to evaluate the potential role of cryptobenthic fishes in coral reef ecosystems. Using frequency of occurrence data, dietary analyses revealed a diverse range of trophic groups, although detritivory (in 10 out of 16 species and 39.3% of individuals) and carnivory (5 of 16 species and 40.5% of individuals) clearly dominate as trophic modes. Herbivory (1 species; 2.4% of individuals) is only a minor component in the community trophic structure. Of the 18 dietary categories identified, detritus and copepods were the only constituents represented in all 16 species examined. Although the degree of dietary specialization varied among taxa, the 2 most abundant species, Eviota queenslandica and Istigobius goldmanni, utilised the broadest range of dietary items. Morphology reflected the trophic partitioning among fishes: carnivores were invariably < 28 mm total length (TL) and had gut-length ratios (GLRs) of < 0.5; detritivores were all > 38 mm TL with GLRs generally exceeding >1.0. The trophic composition and numerical strength of the cryptobenthic fish fauna suggests that cryptobenthic reef fishes have the potential to make a significant contribution to reef trophodynamics along a number of trophic pathways. This prompts a re-evaluation of the roles of reef fishes in the functioning of coral reefs, particularly those related to the recycling of primary production through detrital pathways.

Evolution of long-toothed fishes and the changing nature of fish–benthos interactions on coral reefs

“…Indeed, detritus is ubiquitous in aquatic systems and some ingestion is almost inevitable. Approximately a quarter of extant reef fishes include some detritus in their diet 9,30 and similar consumption of detritus is likely to have occurred in the past, as morphologically 'cryptic' facultative detritivory. In contrast to facultative detritivory, specialized reef-based detritivory is much more restricted.…”

“…Considering facultative and specialized detritivores together, on many coral reefs, detritivores outnumber algal-eating herbivores in terms of both the number of species and their densities 9,30 .…”

“…Today, specialized detritivores constitute a major component of coral reef fish communities, and detritus is the basis of a key pathway for primary production to pass up the food chain via fishes 9,30 . Considering facultative and specialized detritivores together, on many coral reefs, detritivores outnumber algal-eating herbivores in terms of both the number of species and their densities 9,30 .…”

A quantitative assessment of the cryptobenthic fish assemblage at deep littoral cliffs in the Mediterranean

“…To gain a full understanding of how a fish assemblage is composed and structured on hard littoral bottoms, a study of small cryptobenthic and epibenthic species using destructive techniques is required. Quantitative studies on cryptobenthic fish communities are surprisingly rare worldwide and restricted to coastal reefs with depths of mainly 15 to 20 m (Prochazka 1998, Ackerman and Bellwood 2000, 2002, Willis 2001, Depczynski and Bellwood 2003, Smith-Vaniz et al 2006, Beldade et al 2006, Beldade and Gonçavles 2007, Kovačić et al 2012. No quantitative research on cryptobenthic fish has been performed at or below 40 m depth (Kovačić et al 2012), while only recently the methodology for the quantitative research at circalittoral depths was proposed by Glavičić and Kovačić (2016).…”

Ontogeny of microhabitat use and two-step recruitment in a specialist reef fish, the Browncheek Blenny (Chaenopsidae)

“…Though they have historically been underrepresented in reef diversity and biomass studies (due to their small size and difficulty in field identification), cryptobenthic fishes are significant contributors to reef microcarnivory and detritivory (Kotrschal and Thompson 1986;Depczynski and Bellwood 2003) and constitute a significant portion of reef fish biodiversity (Smith-Vaniz et al 2006). Many of these less conspicuous specialists almost certainly follow a similar ''two-step'' recruitment path, but few data are available documenting this transition Gonçalves and Faria 2009).…”